An electrical connector (hereinafter referred simply to as a connector) for a flexible flat cable such as a flexible printed circuit (FPC) or a flexible flat cable (FFC) is mounted on a printed wiring board. In a housing of the connector, a plurality of contacts that are electrically connected to the printed wiring board are provided. By electrically connecting these contacts to the conductors of the flat cable, the flat cable is connected to the printed wiring board.
In the connector, in order to keep an electrically connected state between the flat cable conductors and the contacts, typically, the flat cable is clamped by the contacts, and each of the contacts is made in a state of being pressed against the flat cable conductor by utilizing the elasticity of the contact itself. When the flat cable is inserted into the connector, the insertion of the flat cable should be prevented from being hindered by the resistance of contacts. For this purpose, a ZIF (Zero Insertion Force) type connector that keeps the contacts in an opened state is available.
In such a ZIF type connector, the contact having been in an opened state is deformed and operated by an actuator, whereby the contact is pressed against the flat cable conductor. A known ZIF type connector, for example, is disclosed in Japanese Patent Laid-Open No. 2002-270290. As shown in FIG. 5, a known contact 1 is a flat and having a substantially H-shape. The contact 1 includes contact arms 2 and 3, a pivot 4, a lever 5, and a base 6. When an actuator 7 is turned clockwise, the lever 5 is displaced upward by a cam 8, and the pivot 4 of the contact 1 is elastically deformed. Thereby, a flat cable 9 is clamped between the contact arms 2 and 3, and is electrically connected to the contact 1.
However, conventional contacts, as described above, have certain problems.
In the contact 1, the contact arm 2 and the lever 5 form one beam, and the contact arm 3 and the lever 6 also form one beam. Therefore, in order to reliably clamp the flat cable 9 between the contact arms 2 and 3, the displacement of the lever 5 caused by the elastic deformation of the pivot 4, produced by the operation of the actuator 7, must be transmitted efficiently to the contact arm 2. However, when the lever 5 is displaced upward by the operation of the actuator 7, the displacement of the contact arm 2 is restricted by the contact of the contact arm 2 with the flat cable 9. Thereby, the contact arm 2 is subjected to a reaction force from the flat cable 9, so that the lower portion of the pivot 4 is raised, and lifts from a printed wiring board 100. Therefore, the displacement of the contact arm 2 becomes smaller than the displacement inherently produced in the contact arm 2 by the operation of the actuator 7, along with the elastic deformation produced in the contact arm 2 and the lever 5. As a result, depending on the thickness of the flat cable 9, the force for pressing the contact arm 2 against the flat cable 9 (referred to as a contact pressure) may be insufficient To solve this problem, it is thought that the distance from the pivot 4 to the point of application of the force in the actuator 7 is increased by lengthening the lever 5 to increase the clamping force for the flat cable 9 between the contact arms 2 and 3, or the rigidity of the lever 5 is enhanced. However, in such a design, the size of the contact 1 is increased, or the length in the front-back direction thereof is increased. As the sizes of various pieces of electrical and electronic equipment decrease, the connector especially requiring a large mounting area on the printed wiring board 100 is also required to be made small in size. The increased size and rigidity of the contact 1 are unfavorable because they hinder the decrease in size of connector. Also, in the case where the rigidity of the lever 5 is enhanced, the force required for the operation of the actuator 7 increases, so that the operability of the actuator 7 may be degraded.
The connector is required to be formed so that the height, thereof in the state of being mounted on the printed wiring board 100, is decreased as far as possible (this is called low-profile). The conventional flat and substantially H-shaped contacts are also formed so as to meet this requirement. However, if the lever 5 is lengthened, the displacement on the rear end side of the lever 5 at the time when the lever 5 is operated by the actuator 7 increases, which hinders the contact from being low-profile.
Also, the contact 1, the cam 8 of the actuator 7, and the flat cable 9 vary in dimensions. By the variations in the gap between the lever 5 and the base 6 of the contact 1, and the variations in dimension in the major axis direction of the cam 8, the upward displacement of the lever 5 at the time when the actuator 7 is operated varies. Also, by the variations in the gap between the contact arms 2 and 3 of the contact 1, the displacement of the contact arm 2 caused by the displacement of the lever 5 varies. Further, the variations in thickness of the flat cable 9 also lead to the variations in the relative displacement of the contact arm 2 with respect to the flat cable 9. The variations in these dimensions are amplified according to the lengths (lever ratio) of the contact arms 2 and 3 and the lever 5. As a result, the variations in these dimensions lead to the variations in contact pressure of the contact arm 2 against the flat cable 9 for each contact 1 or each connector. If the contact pressure is insufficient, the flat cable 9 may not be clamped reliably by the contact 1. Also, if the contact pressure is excessive, the surface of the contact point of the contact 1 may roughen and electrical conductivity may become impaired. In the case where the contact pressure is excessive, the contact arm 2 and the lever 5 may be deformed plastically, exceeding the elastic deformation zone. In this case, when the flat cable 9, having been clamed by the contact 1, is unclamped by the operation of the actuator 7, for example, at the time of maintenance, the gap between the contact arms 2 and 3 does not widen sufficiently. As a result, even if an attempt is made to insert the flat cable 9 again, the flat cable 9 may interfere with the contact arms 2 and 3. Also, if the lever 5 has been deformed plastically, when the flat cable 9 is inserted between the contact arms 2 and 3 again after being unclamped, and is clamped by operating the actuator 7, the contact arms 2 and 3 may not exert a sufficient clamping force on the flat cable 9.